Geneva gear sectors mounted on a common shaft for the stepwise rotation of the switching contacts of rotary switches

ABSTRACT

A driving mechanism for the stepwise rotation of the switching contacts of a rotary switch through angles of different magnitudes by means of different maltese crosses and driving members cooperating with said crosses, said driving members being driven by a common shaft through sets of cooperating normal toothed wheels and cooperating elliptical-toothed wheels said sets of cooperating toothed wheels having equal mean transmission ratios.

United States Patent Inventor Gerardus A. Van Riemskijk Nijmegen, Netherlands A ppl. No. 10 438 Filed Feb. 11, 1970 Patented Aug. 3, I971 Assignee Smit Nymegen Electrotechnische Fabrienken N. V. Netherlands GENEVA GEAR SECTORS MOUNTED ON A COMMON SHAFT FOR THE STEPWISE ROTATION OF THE SWITCHING CONTACTS 0F ROTARY SWITCHES 2 Claims, 3 Drawing Figs.

US. Cl 200/153 PA, 74/436, 200/11 TC, 74/84 Int. Cl H0111 3/44, HOlh 3/40 Field of Search 200/153 P,

153 PA, 1 1 TC; 74/436, 84,116, 63, 373

[56] References Cited UNITED STATES PATENTS 2,240,324 4/1941 Bert 74/436 3,204,176 8/1965 Wilson,Jr... 200/153 PA FOREIGN PATENTS 184,994 3/1956 Austria 200/153 PA 656,067 8/1951 Great Britain. 74/436 1,276,192 8/1968 Germany 200/11 TC Primary Examiner- Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Auomeylmirie, Smiley, Snyder and Butrum ABSTRACT: A driving mechanism for the stepwise rotation of the switching contacts of a rotary switch through angles of different magnitudes by means of different maltese crosses and driving members cooperating with said crosses, said driving members being driven by a common shaft through sets of cooperating normal toothed wheels and cooperating ellipticaltoothed wheels said sets of cooperating toothed wheels having equal mean transmission ratios.

PATENTED AUB 3-1971 3597559 L 3 s 15 14 13 1 u 20 21 III FIG.]

IN V E NTOR ATTORNEY GENEVA GEAR SECTORS MOUNTED ON A COMMON SHAFT FOR THE STEPWISE ROTATION OF THE SWITCHING CONTACTS OF ROTARY SWITCHES The invention relates to a driving mechanism for the stepwise rotation of the switching contacts of a rotary switch through angles of different magnitudes by means of sectors of different maltese crosses (also know as Geneva gears), said sectors cooperating each with an individual rotatable driving member and becoming operative one after the other, all sectors being positively coupled with the rotary shaft of the switching contacts and all driving members being positively coupled with a common driving shaft.

A driving shaft of this kind is disclosed in the British Pat. No 1,054,195. In this known driving mechanism, which is used for rotation of the rotatable switching contacts of the tap changer for a regulating transformer, in which in one or more places along the circular path of the rotatable switching contacts the angular distance between two adjacent fixed contacts in other places, the driving members for the different sectors of the maltese crosses are rigidly connected with each other. This construction has the disadvantage that the switching contacts, when rotated through a greater angle, means during the operation of the maltese cross having the smaller number of angular steps per revolution, are moved from one to the other fixed contact with greater angular velocity than when they are rotated through a smaller angle, that means during the operation of the greater number of angular steps per revolution, so that the switching process, which strongly depends on the angular velocity of the switching contacts, can be liable to great local difference.

The invention has the object to provide a driving mechanism of the kind mentioned having a multiple maltese cross driving mechanism, in which the disadvantage of the known driving mechanism is avoided in a simple manner. It consists in that the driving members are mounted for rotation one in respect of the other and are coupled with the driving shaft via individual sets of cooperating toothed wheels, the mean transmission ratios of said sets of toothed wheels being equal and at least one of said sets of toothed wheels comprising cooperating elliptical toothed wheels. By means of elliptical-toothed wheels the transmission ratio can be considerably varied within each revolution, so that thereby the angular velocity of the maltese cross sector driven by the driving member can be easily adapted to the required circumstance.

For a rotatable tap changer having fixed contacts which in one or more places lie at a greater angular distance from one another than in the other places it may be advantageous to use a driving mechanism, in which the sets of toothed wheels provided between the driving shaft and the driving members are so constructed and so cooperate with each other as to ensure that the mean transmission ratios occuring during the active strokes of the driving members are inversely proportional to the angular steps of the maltese crosses cooperating with the respective driving members. In that case the mean switching velocities in all places between two fixed contacts of the tap changer will be substantially equal, that means will be independent from the angular distance between said contacts.

The invention will be further elucidated with the aid of the drawing. In the drawing:

FIG. 1 isan axial sectional view ofa driving mechanism constructed in accordance with the invention and comprising two sectors of two different maltese crosses, 1

FIG. 2 is a cross-sectional view taken on line 11-11 in FIG. 1 and FIG. 3 is a cross-sectional view taken on line III-III in FIG. 1.

In the drawing the reference numeral 1 designates a driving shaft. This shaft may be the crankshaft of an energy accumulator of the crankshaft-spring-type which is generally used in rotary tap changers for regulating transformers. The driving shaft 1 is supported rotatably in stationary plates 4 and 5 by ball bearings 2 and 3. Mounted on the driving shaft 1 is an elliptical-toothed wheel 6, which rotates about one of its foci and cooperates with an elliptical-toothed wheel 7 of equal size and shape. The latter toothed wheel is attached in a focus to a shaft which is mounted for rotation in the plate 4 and an auxiliary plate 11 by ball bearings 9 and 10. Provided on the driving shaft 1 is also a circular-toothed wheel 12 which cooperates with a circular-toothed wheel 13 of the same diameter. The latter toothed wheel is mounted on a shaft 14 which is rotatably supported in the plate 5 and the auxiliary plate 11 by ball bearings 15, 16.

Attached to the shaft 18 provided with the elliptical-toothed wheel 7 is a driving member 17 of a maltese cross driving mechanism, of which the driving pin 17a is adapted to engage slots 18a ofa sector 18 of a maltese cross for 16 angular steps per revolution. Said sector 18 is mounted on a switch shaft which must be rotated stepwise. Furthermore a driving member 20 ofa second maltese cross driving mechanism is attached to the shaft 14 provided with the circular-toothed wheel 13. The driving pin 20a of said driving member is adapted to engage in the slot 21a of a sector 21 of a maltese cross for eight angular steps per revolution. This sector 21 is also attached to the switch shaft 19. The maltese cross sector 18 extends over fourteen of the 16 angular steps and the maltese cross sector 21 has only one of the eight angular steps of the respective maltese cross, of which the remaining portion is suppressed. The two sectors 18 and 21 are so mounted on the shaft 19 as to extend together over an angle of 360.

The elliptical-toothed wheels 6 and 7 are so mounted in respect of each other, that, when the driving pin 17a has penetrated a slot 18a of the maltese cross sector 18 to the maximum extend and thus intersects a radius of said sector at right angles, the elliptical-toothed wheels 6, 7 are each directed with their longest radius extending from the shaft 1 towards the switch shaft 19 to be driven. In said position the shaft 19 is driven with an angular velocity which is somewhat more than twice the velocity that would be produced, when the shafts would have been coupled by circular toothed wheels. It will be apparent that, if the elliptical-toothed wheels 6, 7 are constructed in such a way, that the mean transmission ratio of said toothed wheels 6, 7, during the active stroke of the driving member 17, is 2:1, that means twice the transmission ratio of the toothed wheels l2, 13, which is lzl, the mean angular velocity, with which the switch shaft 19 is rotated by the driving member 17, 17a and the maltese cross sector 18 through the small angular distance, will be equal to the mean angular velocity, with which the switch shaft 19 is rotated by the driving member 20, 20a and the maltese cross sector 21 through the large angular distance.

It is observed that also the toothed wheels 12, 13 may be formed as elliptical-toothed wheels. The maltese crosses may each consist of two or more sectors, which alternate in the circle with sectorsof one or more other maltese crosses. By means of the shape of the toothed wheels the angular velocities of the driven switch shaft can be locally adapted to the requirements of the switching process and the mechanical construction of the driving mechanism.

What we claim is:

l. A driving mechanism for the stepwise rotation of the switching contacts of a rotary switch through angles of different magnitudes by means of sectors of different maltese crosses, said sectors each cooperating with an individual rotatable driving member and becoming operative one after the other, all sectors being positively coupled with the rotary shaft of the switching contacts and all driving members being positively coupled with a common driving shaft, characterized in that the driving members are mounted for rotation one in respect of the other and are coupled with the driving shaft via individual sets of cooperating toothed wheels, the mean transmission ratios of said sets of toothed wheels being equal and at least one of said sets of toothed wheels comprising cooperating elliptical-toothed wheels.

mission ratios occuring during the active strokes of the driving members are inversely proportional to the angular steps of the Maltese crosses cooperating with the respective driving members. 

1. A driving mechanism for the stepwise rotation of the switching contacts of a rotary switch through angles of different magnitudes by means of sectors of different maltese crosses, said sectors each cooperating with an individual rotatable driving member and becoming operative one after the other, all sectors being positively coupled with the rotary shaft of the switching contacts and all driving members being positively coupled with a common driving shaft, characterized in that the driving members are mounted for rotation one in respect of the other and are coupled with the driving shaft via individual sets of cooperating toothed wheels, the mean transmission ratios of said sets of toothed wheels being equal and at least one of said sets of toothed wheels comprising cooperating elliptical-toothed wheels.
 2. A driving mechanism according to claim 1, characterized in that the sets of toothed wheels provided between the driving shaft and the driving members are so constructed and so cooperate with each other as to ensure that the mean transmission ratios occuring during the active strokes of the driving members are inversely proportional to the angular steps of the Maltese crosses cooperating with the respective driving members. 